1. Field of the Invention
The present invention is directed to a butterfly type valve construction and more specifically to a butterfly type valve construction having sealing means and adjustable locking means.
2. Prior Art
Butterfly valves are old and well known in the art and generally consist of a circular plate pivoted diametrically within a cylindrical conduit. Most prior art constructions utilize a metal-to-metal contact between the plate and conduit. While accurate tolerances to prevent undue leakage can be achieved initially, excessive leakage invariably occurs due to wear between the plate and conduit. Proposals have been made in the past to provide the conduit with an offset surface for engagement by the opposed surfaces of the valve plate. However, the use of such offset valve seats protruding into the conduit restrict the flow of fluid through the conduit in an objectionable manner.
While some form of locking device has been provided in the past for a valve operating shaft. Such locking devices were generally rigid with the conduit so that it was impossible to compensate for wear of the valve members. In other words, the valve member would always be locked in the same place even though the valve no longer was disposed in close fitting relation with the seat thereby causing undue leakage.